It has long been customary in the art to use combinations of organic and inorganic raw materials to produce combination materials, for example, for filling rubbers or thermoplastics with inorganic fillers, for pigmenting lacquers with inorganic pigments or for the manufacture of molding materials. These rubbers, thermoplastics and molding materials are mainly solid substances in which the fillers, once incorporated, maintain a virtually unchanged degree of distribution. In contrast, polyols conventionally used in polyurethane chemistry are liquid substances which change into solids or rubbery materials only after the reaction with the polyisocyanates.
Inorganic fillers generally have specific gravities above 2 whereas most polyols have specific weights of about 1. Suspensions of inorganic pigments in polyols will, therefore, settle out even if the pigments are very finely milled. This is particularly true if the polyols have relatively low viscosities, a condition generally necessary for processing purposes.
This characteristic constitutes a serious obstacle to the use of inorganic fillers in polyurethane chemistry. There is, therefore, an understandable desire to have such suspensions available in a form which is stable in storage so that they need not be mixed again during storage or before use.
Polyethers modified with vinyl polymers (including vinyl compounds containing carboxyl groups, e.g., acrylic acids) are discussed in U.S. Pat. Nos. 3,383,351; 3,304,273; 3,523,093; 3,110,695; and German Pat. No. 1,152,536. These patents, however, do not discuss the use of fillers.
It was, therefore, an object of the present invention to provide stable suspensions of inorganic fillers in polyols of the kind used for the production of polyurethanes.